Preparation of methyl vinyl ketone



Patented Sept. 16, 1941 FICE- 2,256,149 PREPARATION or METHYL vnwr. KETDNE John B. Long, Akron, Ohio, assignor to Wingfoot Corporation, Wilmington, M, a corporation of Delaware No Drawing. Application June 4, 1940, Serial No. 338,743

Claims.

This invention relates to an improved method of preparing methyl vinyl ketone and, more par ticularly, to the treatment of 3-chlor-2-butanone to produce such methyl vinyl ketone. Attempts to'prepare methyl vinyl ketone by removing hydrogen chloride from 3-chlor-butanone by pyrolysis in the presence of catalysts have been unsuccessful. It has now been found that if the 3-chlor-2-butanone be first converted to 3-acetoxy-2-butanone, the latter compound can readily be pyrolyzed to yield the desired substance.

The conversion of the 3-chlor-2-butanone to the acetoxy compound can be brought about, for example, by treatment with an alkali metal acetate in acetic acid, sodium acetate in acetic acid being found effective." The reaction proceeds in accordance with the following equation:

c1 DOC-CH;

The 3-acetoxy-2-butanone is then subjected to pyrolysis at temperatures .which may range from 400-700 C. but preferably from 500550 C., with best results obtained in the vicinity of 525 C. A catalyst may be present, such as copper. The product of pyrolysis is then fractionated, preferably under less than atmospheric pressure, say that corresponding to 50-60 mm. mercury, to recover the methyl vinyl ketone. The reaction involved is the following:

To illustrate the invention, the following ex ample is given, although it will be understood that the invention is not limited to the conditions therein set forth.

A mixture of 3 mols sodium acetate, 6 mols acetic acid and 3'mols 3-chlor-2-butanone was refluxed for a day. The salt which formed was filtered oil. and the product was isolated by freetional distillation of the filtrate. The 3-acetomr- ,Z-butanone thus prepared was then througha 28mm.Pyrex tubepacked'with copper'turnings,,the tube being heated in a 30" nirnacetoatemperatureof520-5250. One hundred twelve grams oi the acetylated compound were passed through the tubeinanhour. The crude product m then iractionated atatrmospherictogiveayleldotmfigrams of methyl vinyl ketone. More of the ketone can be recovered if the distillation is carried on at reduced pressure, a pressure corresponding to 50-60 mm. of Hg being suitab The conditions given above can-be varied, of course, various contact catalysts being available besides those mentioned and the speed of passage through the heated tube and the temperature being adjustable to give the best results.

Also, the method of preparing the 3-acetoxy-2- butanone from the 3-ch1or butanone may be varied, as by employing other acetylating agents, such as potassium acetate in acetic acid or in alcohol. Other acetates in other non-aqueous solvents therefor may also be employed.

While there has been described above a certain preferred embodiment of the invention, it will be apparent that various changes and modifications may be made therein without departing which comprises and then heating the acetate at a temperature C. to obtain the I from the spirit of the invention. Accordingly, the invention is to be limited only by the al pended claims in which What I claim is; 1. A method of preparing methyl vinyl ketone which comprises acetylating 3-chlor-2-butanone and pyrol'yzing the resulting product to obtain the methyl vinyl ketone.

2. A method of preparing methyl vinyl ketone acetylating 3-chlor-2-butanone' between about 400 and 700 methyl vinyl ketone.

3.- The method which comprises treating 3- chlor-2-butanone with analkali metal acetate in acetic acid, heating the acetate so formed to a temperature between about 400 and 700 C. and

distilling the productto obtain methyl vinyl ke- Y 46 4. The. method which comprises treating, 3-

chlor-z-butanone with sodium acetate in acetic acid to form 3-acetoxy-2-butanone, heating the acetate to a temperature between about 500 and 550 C. to splitoflf acetic acid and recovering methyl vinyl ketone from theproduct.

5. The method which comprises treating 3- chlor-2-butanone with. potassium acetate in" acetic acid to form 3-acetoxy-2-butanone, heattemperature between about 0. to split ofl. acetic acid and re.-

covering methyl vinyl ketone iron the product.

7 it is intended to set forth' all features of patentable novelty residing there- 

